Touch screen devices have become the dominant platform for mobile computing; however, the lack of tactile feedback on these devices requires a high level of visual attention to select targets accurately. Input is particularly challenging when the user is in motion, a state that can be thought of as causing situational impairments. Situational impairments may be caused by a variety of factors including vibration, divided attention, diverted gaze, body motion, awkward postures, cold temperatures, clothing, rainwater, glare, uneven terrain, ambient noise, or encumbering baggage. The challenges of situational impairments are exacerbated for mobile text entry on virtual keyboards because of the many repeated targeting actions that take place in quick succession.
A significant contextual factors affecting mobile device use may be a user's hand posture with which he or she manipulates a mobile device. Hand postures including grip, one or two hands, hand pose, the number of fingers used, and so on may significantly affect performance and usage of mobile devices. For example, the pointing performance of index fingers is significantly better than thumbs, as is pointing performance when using two hands versus one hand. Similarly, the performance of a user's dominant hand is better than that of his or her non-dominant hand.